Together we stand, divided......

I think it would be a great shame if Scotland seceded from the Union, but more to the point, could they legally do so? The 1707 Act of Union abolished the Scottish parliament, and the current one is a devolved parliament which acts under the authority of Westminster. It could therefore be argued that it has no power to unilaterally make any such decision. Of course, if Westminster agreed, that would be a whole different matter. But let's hope the question doesn't arise, eh?